Doxygen is a documentation system for C++, IDL (Corba, Microsoft, and
KDE-2 DCOP flavors) and C. It can help you in various ways:

It can generate an on-line documentation browser (in HTML) and/or an
off-line reference manual (in ) from a set of documented source
files. There is also support for generating output in RTF (MS-Word),
Postscript, hyperlinked PDF, compressed HTML, and Unix man pages. The
documentation is extracted directly from the sources, which makes it
much easier to keep the documentation consistent with the source code.

Doxygen can be configured to extract the code structure from
undocumented source files. This can be very useful to quickly find
your way in large source distributions. The relations between the
various elements are be visualized by means of include dependency
graphs, inheritance diagrams, and collaboration diagrams, which are
all generated automatically.